1. Field of the Invention
The present invention relates to a porous, in vivo implantation material in which normal tissue growth is fostered. More particularly, the vivo implantation material is a sintered combination of polytetrafluoroethylene fibers and resin having void space of 50 to 90 percent.
2. Prior Art
The present inventor has developed a number of in vivo implantable materials utilizing polytetrafluoroethylene (PTFE) as a base resin. The PTFE resin is highly suitable for in vivo implantation due to its low incidence of rejection by the surrounding host tissue. However, in this field of research, it has been found that the intended site of in vivo implantation defines the form of material to be used. Thus, some applications require supple thin sheets having low Young's modulus of elasticity, some require tubes of high flexibility and flexural fatigue resistance, while others require rigid, solid blocks of material that can be machined or carved. In other words, the human body comprises bone and tissue arranged in such a manner that different mechanical parameters apply in virtually each possible application of an in vivo implantable material.
Consequently, there has been a continuous search for combinations of materials that can be utilized at specific sites in the body to accomplish a given set of tasks. Typical of one of these materials is the implantable material taught and claimed in U.S. Pat. No. 3,992,725, issued to the present inventor. Prior to that patent, there had not been a suitable, porous material providing for ingrowth of normal body tissues. However, the ingrowth material of that patent is usually black in color, due to the fibers used therein. In addition, the tensile stress behavior, abrasive resistance and flexural fatigue life of that material limits some of its potential uses.
Other work in this field is typified by U.S. Pat. No. 3,556,161, directed to PTFE resin sheets.
My prior U.S. Pat. No. 4,118,532 discloses a wear material suitable for in vivo implantation in which the material is processed to orient the fibers parallel to the surface.
The present invention, however, overcomes these and other deficiencies, as explained more completely hereinafter.